CA1149366A

CA1149366A - Production of tertiary-butylstyrene

Info

Publication number: CA1149366A
Application number: CA000368378A
Authority: CA
Inventors: Glen F. Crum; Samuel J. Paton
Original assignee: El Paso Products Co
Current assignee: El Paso Products Co
Priority date: 1980-01-29
Filing date: 1981-01-13
Publication date: 1983-07-05
Also published as: JPS56155652A; IT8147664A1; IT8147664A0; FR2474482B1; US4291183A; DE3103006A1; GB2068251B; GB2068251A; IT1170666B; MX158078A; JPH0123176B2; FR2474482A1

Abstract

ABSTRACT OF THE INVENTION
This invention provides an improved oxydehydrogenation process for the production of tertiary-butylstyrene which involves the contacting of n vapor phase mixture of tertiary-butylethylbenzene and oxygen with a novel coprecipitated aluminum-calcium-cerium phosphate catalyst composition.
The tertiary-butylstyrene is produced with a high conversion selectivity, and concomitantly there is little or no dialkenylbenzene byproducts produced.

Description

IPRODUCTION OF TERTIARY-sUTYLSTYRENE
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Alkenyl-substituted aromatic compounds are important 'I starting materials for the production of resins, plastics, - I rubbers, solvents, chemical intermediates, and the like.
Processes for the production of alkenyl-substituted aromatic compounds often are characterized by low conversion rates which necessitate the recycle o~f large quantities of Il unconverted charge. Many of the known processes require the !I presence of a large volume of steam or other gaseous diluent which is a cost disadvantage. In some processes the conversion efficiency to alkenyl-substituted aromatic product is diminished because of the formation of a relatively large proportion of carbon oxides and other byproducts.
In one well-known commercial process, C2-C3 alkylaromatic hydrocarbons (e.g., ethylbenzene, ethyltoluene and isopropylbenzene) are converted to the corresponding styrene derivatives by passage of the alkylaromatic hydrocarbon feed l and steam over a Fe2O3 catalyst. The conversion per pass is in I the 35-40~ range, and comparatively high temperatures are needed for the oxidative dehydrogenation reaction.
Illustrative of other oxidative dehydrogenation processes, U.S. 3,299,155 describes a process for the production of alkenylbenzenes which involves contacting a mixture of an ethyl (or isopropyl) substituted benzene compound and sulfur dioxide in vapor phase with a metal phosphate catalyst such as ! calcium phosphate.
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U.S. 3,409,696 describes a proeess which involves contacting an admixture of C2-C4 alkylaromatic hydroearbon and steam at a temperature of 500-650C with a catalyst containing 20-60 weight percent of a bismuth compound (e.g., bismuth oxide) on a calcium phosphate support of which at least 90% of the total pore volume is contributed by pores having a diame-ter of 1000-6000A. f U.S. 3,733,327 describes an oxydehydrogenation proeessl for converting a C2-C6 alkylaromatic eompound to the eorrespond-lng C2-C6 alkenylaromatic compound which comprises eontaeting an admixture of starting material and oxygen at 400-650C
with a cerium phosphate or cerium-zirconium phosphate eatalyst.
U.S. 3,957,897 describes a process for oxydehydrogena-tion of C2-C6 alkylaromatic compounds which involves the use of oxygen, a reaetion zone temperature of 450-650C, a spaee veloeity of 55-2500, and a eatalyst which is at least one of ealeium, magnesium and strontium pyrophosphate. I
ore recently, there has been increasing coneern with !
respeet to the potentially harmful environmental effeets assoeiated with the manufaeture of synthetie resin produets.
In the molding of large shaped artieles, for example, volatile eomponents of a polymerizable monomeric formulation sometimes tend to evaporate from freshly coated mold surfaees which are exposed.
Various means have been contemplated for redueing the ¦l level of fugitive vapors in a synthetic resin manufacturing ¦ plant. One method involves the replacement of volatile monomers ¦¦ of a formulation with monomers which have a lower vapor pressure.

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Thus, it is advantageous to substitute an alkenylaromatic compound such as tertiary-butylstyrene for styrene in a polymerizable formulation which contains the volatile styrene as~
a comonomer.
As a further consideration, it has been found that tertiary-butylstyrene is desirable as a comonomer in the preparation of copolymers or as a curing agent for fiber-reinforced plastics because it improves the moldability of polymerizable formulations and it lessens the mold shrinkage of ¦
molded plastic articles.
The advantages of tertiary-butylstyrene as a comonomer in resin systems has stimulated interest in improved processes for synthesizing -this type of higher molecular weight alkenylaromatic compound.
U.S. 3,932,549 describes a process for preparing tertiary-butylstyrene which comprises reacting tertiary-butylbenzene with ethylene and oxygen at 50-300C in the presence of a catalyst prepared by treating metallic palladium ¦ or a fatty acid salt thereof with pyridine.
20 ~ Other known processes for producing tertiary-butylbenzene involve oxydehydrogenation of tertiary-butylethylbenzene. The type of patent processes described hereinabove for oxydehydrogen ation of C2-C6 alkylaromatic compounds are generally applicable for conversion of tertiary-butylethylbenzene to tertiary-butylstyrene.
However, the chemical reactivity of tertiary-butylethylbenzene under oxydehydrogenation conditions is more complex than that of simpler chemical structures such as ethylbenzene or ethyltoluene. The tertlary-butyl substituAnt , -- 3 il I
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.'~ 3~616 of tertiary-butylethylbenzene under oxydehydrogenation conditions is susceptible to cracking so as to yield methane and a residual isopropenyl substituent on the benzene nucleus.
Consequently, one of the ultimate byproducts of tertiary-butylethylbenzene oxydehydrogenation is a dialkenylbenzene derivative such as isopropenylstyrene.
Because of the presence of two or more polymerizable alkenyl groups, a compound such as isopropenylstyrene tends to undergo crosslinking activity and for~ insoluble byproducts during the high temperature cycles of starting material conversion and product recovery in an oxydehydrogenation process.
Heat exchangers and distillation columns can be rendered inoperative by the deposition of high molecular weight polymeric residues.
Further, the presence of an isopropenylstyrene type of contaminant, particularly a variable quantity of such material, in purified tertiary-butylstyrene can complicate or even prohibit the application of the contaminated tertiary-I butylstyrene product as a comonomer in polymerizable formulations.
Accordingly, it is an object of the invention to provide a process for oxydehydrogenation of C2-C6 alkyl-substituted aromatic compounds to the corresponding alkenyl-substituted aromatic derivatives.
It is another object of this invention to provide a process for converting tertiary-butylethylbenzene to tertiary-butylstyrene under moderate conditions with a high level of starting material conversion and product selectivity.

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9~366 It is another object of this invention to provide a process for converting tertiary-butylethylbenzene to tertiary-butylstyrene with little or no production of dialkenylbenzene byproducts.
It is a further object of this invention to provide a novel catalyst adapted for oxydehydrogenation processes.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.

DESCRIPTION OF THE INVENTION
One or more objects of the present invention are accomplished by the provision of a process which comprises contacting a feed stream containing tertiary-butylethylbenzene and oxygen in vapor phase with a catalyst comprising aluminum-calcium-cerium phosphate.
In a more specific embodiment, this invention provides¦
a process for the production of tertiary-butylstyrene under ¦¦ oxydehydrogenation conditions which comprises contacting a feed I mixture of tertiary-butylethylbenzene and oxygen at a temperature in the range between about 350C and 650C with a coprecipitated aluminum-calcium-cerium phosphate catalyst, wherein the conversion selectivity to tertiary-butylstyrene is at least 80 mole percent, and the selectivity to dialkenyl-benzene is essentially zero mole percent.
A preferred reaction temperature for the oxydehydrogenation reaction is one which is in the range between about 400~C and 600~C

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The feed admixture of tertiary-butylethylbenzene and oxygen can contain quantities of other hydrocarbons which do not ¦ adversely affect the invention o~ydehydrogenation reaction, e.g., compounds such as octane, decene, naphthene, benzene, toluene, pyridine,-thiophene, and the like, which may be present in cc~mercially available alkylbenzenes.

The molecular oxygen component of the feed admixture preferably is present in a quantity between about 0.2-5 moles per mole of tertiary-butylethylbenzene, and most preferably in a molar ratio of 0.8-2:1. The oxygen can be supplied as air, commercially pure oxygen, or air enriched with oxygen.
It is advantageous to include a gasiform diluent in the feed stream. Illustrative of suitable diluents are carbon dioxide, nitrogen, noble gases and steam, either individually or in admixture. The diluent is normally employed in a quantity between about 2-20 moles per mole of tertiary-butylethylbenzene in the feed stream.
The pressure utilized in the vapor phase oxydehydro-¦¦ genation process can be subatmospheric, atmospheric or Il superatmospheric. A convenient pressure for the vapor phase 1I process is one which is in the range between about 1 and 200 psi.
Suitable reactors for the vapor phase process includeeither fixed bed or fluid bed reactors which contain the invention aluminum-calcium-cerium catalyst composition. The process can be conducted continuously or noncontinuously,and the catalyst may be present in various forms such as a fixed bed or a fluidized system.

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, ' i '19366 The residence time (i.e., catalyst contact time) of ¦¦ the feed stream in the vapor phase process will vary in the j~ range of about 0.5-20 seconds, and preferably will average in ~¦ the range between about 1-15 seconds. Residence time refers to the contact time adjusted to 25C and atmospheric pressure. The contact time is calculated by dividing the volume of the catalyst bed (including voids) by the volume per unit time flow rate of the feed stream at NTP.
ll An importan-t aspect of the present invention process 10~ is the use of a novel coprecipitated aluminum-calcium-cerium phosphate catalyst composition. The catalyst exhibits unique properties for the conversion of tertiary-butylethylbenzene to the tertiary-butylstyrene with a high conversion efficiency, and with little or no production of dialkenylbenzene -type of byproducts.
The atomic ratio of metals in the catalyst composition can vary in the range of about 5-20:5-20:1 of aluminum:calcium:
Il cerium. The phosphate component is present in a quantity at ¦¦ least sufficient to satisfy the valences of the metal elements 20 1l in the catalyst.
- ll The catalyst can be prepared by the addition to an I¦ aqueous solution of ammonium phosphate of an aqueous solution of ¦I water soluble compounds of aluminum, calcium and cerium metals, I respectively. Illustrative of water-soluble or partially water-¦l soluble compounds are the chlorides, nitrates and sulfates of aluminum, calcium and cerium.

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In a preferred procedure, the pH of the resultant ¦¦ solution of aluminum, calcium, cerium and phosphate compounds is adjusted to about 7 with an alkaline reagent such as ammonium hydroxide. The coprecipitate which forms is recovered, washed with water, and dried.
It has been found that the activity of the catalyst composition is enhanced if the coprecipitate preparation is calcined in an inert atmosphere at a temperature between about 300~C and 600C for a period of about 1-24 hours.

The coprecipitated aluminum-calcium-cerium phosphate composition described above can be used as the catalyst per se, or the said composition can be combined with a suitable internal diluent or carrier substrate. The carrier substrate is preferably incorporated during the coprecipitate formation step of the catalyst preparation.
The carrier substrate should be relatively refractory to the conditions utilized in the invention process. Suitable I¦ carrier substrate materials include (1) silica or silica gel, !¦ silicon carbide, clays, and silicates including those syntheti-20l cally prepared and naturally occurring,which may or may not be acid treated such as attapulgus clay, china clay, diatomaceous i earth, Fuller's earth, kaolin, asbestos and kieselguhr;

(2) ceramics, porcelain, crushed firebrick and bauxite;
¦ (3) refractory inorganic oxides such as alumina, titanium dioxide, zirconium dioxide, chromium oxide, beryllium oxide, ¦¦ vanadium oxide, cesium oxide, hafnium oxide, zinc oxide, ¦~ molybdenum oxide, bismuth oxide, tungsten oxide, uranium oxide, I magnesia, boria, thoria, silica-alumina, silica-magnesia, ¦I chromia-alumina, alumina-boria and silica-zirconia;

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4) crystalline zeolitic alumino-silica-tes such as naturally occurring or synthetically prepared mordeni-te and/or faujasite, either in the hydrogen form or in a form which has been treated with multivalent cations; and (5) spinels such as MgA12O4, FeA12O4, ZnA12O4, MnA12O4, CaA12O4, and other like compounds having the formula MO A12O4 where M is a metal having a valence of 2.
The catalyst as employed in the invention process can be in the shape of granules, pellets, extrudate, powders, tablets, fibers, or other such convenient physical form.
A preferred catalyst composition of the present invention is one which corresponds to the formula:

Al5-2ocas-2ocel (P04)X

wherein x is a number sufficient to satisfy the valences of the metal components.
The preferred catalyst composition of the present invention is adapted for oxydehydrogenation of hydrocarbon ¦ comPounds such as C3-C10 alkenes, C4-Clo cycloalkenes and C2-C6 alkylaromatic compounds, and has particular advantage for the oxydehydrogenation of tertiary-butylethylbenzene and ethyltoluene under mild oxidation conditions.
The presence of the cerium metal component in an invention aluminum-calcium-cerium phosphate catalyst composition appears to enhance the reactivity of the catalyst, and the presence of the aluminum metal component contributes attrition-resistance and extends the life of the catalyst under hydrocarbon oxydehydrogenation conditions.

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I I _ g I 1, 11~9~66 The following examples are further illustrative of the present invention. The reactants and other specific ingredients are presented as being typical, and various modifications can be derived in view of the foregoing disclosure within the scope of the invention.

EXAMPLE I

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! A solution is prepared by dissolving 25 grams of aluminum nitrate [0.07 M, Al(NO2)3 9H2O], 16 grams of calcium nitxate [0.07 M, Ca(NO3)2-4H~O] and 3 grams of cerium(III) nitrate [0.007 M, Ce(NO3)3 6H2O] in 150 milliliters of water. The solution is blended with 150 milliliters of an aqueous solution of dibasic ammonium phosphate [0.3 M, (NH4)2HPO4] having a pH of 7.6. The pH of the resultant blended solution is adjusted to a pH of 7 with ammonium hydroxide.
The solution is heated to the boiling point, maintained at that temperature for a period of about one hour, and then cooled to room temperature. The solid material which has precipitated is separated by filtration. The recovered precipitate is washed with water, and then dried in a vacuum oven at 120C. The dried solids are calcined at 550C under a ¦ nitrogen atmosphere for a period of 5 hours.

B.
A portion of the calcined solids is ground and sieved to a mesh size in the range of 10-20. A 1 cm3 quantity of the catalyst is charged to an electrically heated reactor, and the reactor is heated to a temperature of about 450C.
An air flow of 10 milliliters/minute and a tertiary-butylethylbenzene (meta:para ratio of 3:97) flow of 1 milliliter/
hour are introduced into the inlet of the reactor. The effluent stream from the reactor is cooled, and the resultan-t liquid components are collected and analyzed by a gas chromatograph/

mass spectrometer system.

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3ti6 ¦ The molar persent conversion of tertiary-butylethyl-¦ benzene is 45.6 and the mole percent selectivity to tertiary-butylstyrene is 86.4. The relative selectivity yield of dialkenylbenzenes is less than about 0.03 mole percent.
When an aluminum-calcium-cerium phosphate catalyst contains Ce(IV) rather than Ce(III) metal component, the yield of dialkenylbenzene byproducts tends to increase.

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XAMPLE II
An aluminum-calcium-cerium phosphate catalyst is prepared in the same manner as Example I, employing an eight-fold increase in the rela-tive proportions of chemical components.
The atomic ratio of the metals in the catalyst composition are in a ratio of 9.8:9.6:1 of Al:Ca:Ce.
A 100 cm3 portion of the catalyst powder (10-20 mesh) is charged to a reac-tor which is a 0.5 inch stainless steel pipe of 24 inch length. The reactor and a part of the feed line are immersed in a molten salt bath.
Variable ~uantities of tertiary-butylethylbenzene between about 30-120 milliliters/hour are fed to the reactor, together with a gas stream consisting of about 400-800 milliliters /
minute of air and about 500-1000 milliliters/minute of nitrogen.
Assay of the liquid products and of the effluent gas from the condenser are employed to calculate the conversion and selectivity results. The reaction conditions and data calculations from 3 runs are sunmarized in the following Table.

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Oxidative Dehydrogenation of Tertiary-butylethylbenzene 1_ 2 3 Hydrocarbon feed rate,g/hr 31 56 83 Mols O2/mol t-BEB 1.09 0.61 ~.41 Mol fraction t-BEB in feed 0.052 0.090 0.127 Reactor temp.,inlet,C 494 465 464 Peak temperature 560 515 505 Liquid hourly space velocity g/g/hr 1.15 2.07 3.06 Conversion, % 49.7 39.8 32.4 tert-Butylstyrene assay % 42.6 35.2 28.8 ~ialkenylbenzenes 0 0 0 Selectivity, mole %
! _ __ CO 3.5 2.7 1.8 l C2 9.2 6.8 5.4 li Light By-products 4.8 2.7 3.2 tert-Butylstyrene 80.6 86.5 88.6 Heavy By-products 1.9 1.3 1.0 !I Dialkenylbenzenes o 0 0 i~ - 14 -

Claims

WHAT IS CLAIMED IS:

1. A process for the production of tertiary-butylstyrene which comprises contacting a feed stream containing tertiary-butylethylbenzene and oxygen in vapor phase with a catalyst comprising aluminum-calcium-cerium phosphate.

2. A process for the production of tertiary-butylstyrene under oxydehydrogenation conditions which comprises contacting a feed mixture of tertiary-butylethylbenzene and oxygen at a temperature in the range between about 350°C and 650°C with a coprecipitated aluminum-calcium-cerium phosphate catalyst, wherein the selectivity to tertiary-butylstyrene is at least 80 mole percent, and the selectivity to dialkenylbenzene is essentially zero mole percent.

3. A process in accordance with claim 2 wherein the feed mixture contains between about 0.2-5 moles of molecular oxygen per mole of tertiary-butylethylbenzene.

4. A process in accordance with claim 2 wherein the feed mixture contains a gaseous inert diluent.

5. A process in accordance with claim 2 wherein the feed mixture contains nitrogen and/or carbon dioxide and/or steam as a gaseous inert diluent.

6. A process in accordance with claim 2 wherein the contact time between the feed stream and the catalyst is in the range between about 0.5 and 20 seconds.

7. A process in accordance with claim 2 wherein the aluminum, calcium and cerium metal elements, respectively, are present in the catalyst in an atomic ratio of about 5-20:5-20:1 and the phosphate component is present in a sufficient quantity to satisfy the valences of the metal elements in the catalyst.

8. A process in accordance with claim 2 wherein the aluminum-calcium-cerium phosphate catalyst is supported on a carrier substrate.

9. A process for the production of binyltoluene which comprises contacting a feed stream containing ethyltoluene and oxygen in vapor phase with a catalyst comprising aluminum-calcium-cerium phosphate.

10. A process in accordance with claim 9 wherein the conversion selectivity to binyltoluene is at least 80 mole percent.

11. A coprecipitated catalyst composition adapted for oxydehydrogenation reactions, which catalyst composition corresponds to the formula:
Al5-20Ca5-20Ce1(PO4)x wherein x is a number sufficient to satisfy the valences of the metal elements in the catalyst.

12. A coprecipitated catalyst composition in accordance with claim 11 wherein the cerium metal is substantially in the plus three valence state.

13. A coprecipitated catalyst composition in accordance with claim 11 in combination with a carrier substrate.